Figure 3: After the extraction of the VOIs by the level set algorithm (a), the partial volume effect on the boundaries of the Lv is isolated with an intensity threshold-based segmentation using the OTSU method (b) to calculate the optimal threshold on the histogram. This threshold is used to separate the gray level intensities into two clusters to form a binary image. The figure shows the effect of the intensity thresholding with a threshold value of 225, where the retained Lv voxels were colored in black. Lateral ventricles (Lv). Volumes of interest (VOIs).